Helped a guy move a boat today (motoring only) and noticed that the tachometer was constantly fluctuating between around 1500 up to 2500 and down again to 2000...It did this for the 20 mins or so we were running.
The engine seemed to maybe vary it's pitch slightly but not to the extent of the reading.
Any ideas, is it just a tachometer fault or engine related?
Sounds like a loose wire.
I recon NSW onto it, check wiring at the alternator, at least when mine played up that's where the trouble was